1. Field of the Invention
The present invention relates to an information recording/reproducing apparatus and, more particularly, to an information recording/reproducing apparatus for recording on and reproducing from a discoidal recording medium.
2. Description of the Prior Art
Hitherto, as such a kind of apparatuses, there are magnetic disk, optical disk, photo-magnetic disk, etc. An explanation will be made as an example with respect to the optical disk.
In the case of recording information on the optical disk which is rotating at a constant angular velocity, the minimum pit diameter is limited due to limitation of the diameter of a laser beam which is used for recording and reproduction. The recording and reproducing conditions are the severest at the innermost rim where the linear velocity is the slowest. The transfer rate of the recording data is determined by the pit diameter and the rotating speed of the disk at the innermost rim. In this case, the recording density deteriorates as the recording position approaches the outer periphery. As a system of preventing this problem, there is known what is called a CLV (Constant Linear Velocity) system in which the linear velocity is optimized in consideration of the pit diameter and the discoidal recording medium is rotated such that the linear velocity becomes constant, thereby making constant the recording density on the disk surface and the recording disk is most efficiently used with respect to the recording density. However, this CLV system has the following drawback. Namely, in the case where the disk is accessed at the positions of largely different diameters such as from the inner rim to the outer rim, or the like, it takes a time until the rotating speed of the discoidal recording medium becomes the constant linear velocity because of the inertia or the like of the medium, so that the access time becomes longer than that of what is called a CAV (constant Angular Velocity) system in which the angular velocity is constant, or the like.